1. Field of the Invention
The present invention relates generally to finishing machines and, more particularly, to tumbler-type finishing machines wherein an open-end drum is supported for rotation about an axis, and the orientation of the axis is controllable to facilitate the optimum performance of a finishing cycle.
2. Prior Art
Many surface finishing operations such as deburring, burnishing, descaling, cleaning, and the like can be conducted expeditiously in a finishing machine. Two basic types of finishing machines are in common use, namely, vibratory machines and tumbler machines. Both types of machines employ receptacles adapted to receive finishing media and workpieces to be finished. Vibratory machines are provided with drive systems for vibrating their receptacles to impart a precessing type of movement to the contents of the receptacles whereby workpieces and media are circulated together in the presence of vibration to cause the media to impart a finishing action to the workpieces. Tumbler machines are provided with drive systems for rotating their receptacles to impart a tumbling-type movement to the contents of the receptacles whereby the media is caused to impact the workpieces to effect a finishing action.
Vibratory finishing machines are of essentially two types, namely, bowl machines and tub machines. In bowl machines, the receptacle is of an essentially annular configuration and provides a toroidal-shaped, upwardly opening trough through which media and workpieces churn and precess as a vertically oriented drive system vibrates the bowl. In tub machines, the receptacle is ordinarily of elongate configuration and defines an elongate, upwardly opening trough wherein media and workpieces are caused to churn and precess under the influence of an essentially horizontally oriented drive system. The referenced Bowl Machine and Tub Machine Patents provide examples of these two types of vibratory finishing machines.
Tumbler machines are of essentially two types, namely, fixed axis machines and tiltable axis machines. Fixed axis machines may have their axes oriented either horizontally or at a predetermined angle of inclination. Where the fixed axis extends horizontally, the finishing receptacle ordinarily takes the form of a barrel having closed ends with both ends being journaled for rotation to securely support the barrel. Where the axis is oriented in an inclined attitude, the receptacle ordinarily takes the form of a drum having an open, upwardly facing end. The drum is supported for rotation on a shaft cantilevered to the closed lower end of the drum. Examples of these two types of fixed axis machines are provided by the referenced Horizontal Axis Tumbler and Inclined Axis Tumbler Patents.
Tiltable axis tumbler machines are preferred over other types of finishing machines for a number of types of finishing operations, particularly those where finishing conditions need to be controllably varied during different stages of their finishing cycles. Tiltable axis tumblers are typically provided with a drum-type finishing receptacle having an open end and a closed end. The drum is typically supported for rotation by means of a shaft which is cantilevered to the closed end of the drum. An advantage of tiltable axis tumblers is that the open end of the drum may be oriented in an upwardly facing attitude for loading, an inclined or horizontal attitude for performing a finishing operation, and a downwardly facing attitude for unloading. An example of a tiltable axis tumbler machine is provided by the referenced Tiltable Axis Tumbler Patent.
As is brought out in introductory portions of the referenced Inclined Axis Tumbler Patent, it is known in the art to provide a tiltable axis tumbler with a door for closing the open end of its drum. When a finishing operation has been completed, the drum is oriented with its discharge door facing upwardly, at which time the door is unlocked and a crane is used to lift the door from the open end of the drum. The drum is then rotated to orient its open end in a downwardly facing attitude to effect unloading. As is emphasized in the referenced Inclined Axis Tumbler Patent, the procedures involved in orienting the drum in an upwardly facing attitude, positioning a crane for removal of the door, effecting door removal, and reorienting the drum for discharge are complicated and time-consuming, and accordingly significantly increase the cost of a finishing cycle.
Prior to the existence of the present invention, the largest known tiltable axis tumblers provided a maximum capacity of about 20 cubic feet. These machines were designed to receive maximum loadings of about 150 to 200 pounds per cubic foot. Tiltable axis tumblers having a capacity approaching 30 cubic feet and larger, and adapted to receive loadings of up to 400 pounds per cubic foot have not been available, although machines of this large capacity would clearly be desirable. For example, loadings on the order of 400 pounds per cubic foot are desirable for many types of finishing operations in order that steel shot and other relatively heavy, fast-acting media can be used. In part, it is believed that large capacity tiltable axis tumblers have not been available because prior tiltable axis tumbler designs are not applicable to the scale of the tumblers contemplated here.
Many tiltable axis tumblers of the open end type are provided with an inherently unbalanced drum and drive system. The problem of imbalance is frequently magnified quite significantly when the drum is loaded with workpieces and finishing media. In large capacity machines, unbalanced systems of the type commonly used in smaller capacity machines would require the provision of unwieldy large components to withstand the force imbalance.
While previously proposed tiltable axis tumblers have been provided with variable-speed drive systems and with power-operated, drum-axis orientation controls, substantial amounts of time have been occupied in opening the drum, loading the drum, closing the drum, orienting the drum for finishing, adjusting speed of rotation to achieve a desired type of finishing action, stopping and reorienting the drum for cover removal, removing the cover, and reorienting the drum for discharge. Prior tumbler finishing machines have not been able to be loaded and unloaded rapidly, particularly where these machines have had drums of relatively large capacity provided with a heavy and unwieldy cover.
Finishing machine receptacles are normally lined with a relatively resilient material to cushion the impact of finishing media and workpieces against the walls of the receptacle. The lining is worn away under the repeated impact forces of the finishing media and workpieces. While lining materials having relatively long lives are employed in these receptacles, after a substantial amount of operation the receptacles must be removed from the machines and relined. In many finishing machine installations, a spare, relined receptacle is kept at hand so that when a receptacle lining needs to be replaced, the spare, relined receptacle is substituted for the worn receptacle and the worn receptacle is returned to the manufacturer for relining. Where finishing receptacles are of relatively large capacity, the procedure of removing a receptacle from a finishing machine and replacing it with a relined receptacle can be time consuming. Many previous tumbler machines have had drum-mounting systems that are not well adapted to facilitate drum removal and replacement.
During the operation of a tumbler, components of the machine are subjected to numerous transient loads and shocks. As material contained when the receptacle continuously rises and falls within the receptacle, repeated shocks are transmitted from the receptacle through its drive system to other components of the machine. Where relatively large receptacles having high loading capabilities are employed, the several startings and stoppings of drum rotation which may be employed during a given finishing cycle add to the shocks imposed on the drive system and on other supporting components. As the drum is tilted to different attitudes during a finishing cycle, corresponding movements are imparted to the contents of the drum, which result in the falling of contents within the drum and the imposition of still further transient loads and shocks on the drive system and related components. While the need for a shock absorbing drive in tumbler machines is noted in the referenced Horizontal Axis Tumbler Patent, the type of shock absorbing drive system described in this patent has not proved entirely effective in isolating transient loads in more heavy-duty, large capacity tiltable axis tumblers.
A further problem encountered with tiltable axis tumblers is that of providing a drive system which is not position sensitive and which can, therefore, be used to rotate the drum regardless of the orientation of the drum rotation axis. Still another problem is that of providing a drive system that is not damaged by such finishing liquids and chemicals as may be utilized in conjunction with the operation of the finishing machine.